Over 1,000 people, including as many as 350 infants, could have been exposed to tuberculosis by an infected nurse in the maternity wing of California’s Santa Clara Valley Medical Center. The infants will now be monitored for signs of active tuberculosis.

According to the San Jose-based hospital, apart from the 350 infants, 308 employees and 368 parents, primarily mothers, were potentially exposed to TB between August and November of this year.

The Center’s officials say they have identified all of the patients, staff members, and visitors who were at SCVMC’s Mother & Infant Care Center during that period and are currently contacting them.

“While the risk of infection is low, the consequences of a tuberculosis infection in infants can be severe. That’s why we decided to do widespread testing and start preventative treatments for these infants as soon as possible,” said Dr. Stephen Harris, chair of pediatrics, according to an official press release.

The nurse, whose name is not being disclosed, was put on leave before her diagnosis was confirmed. It appears that she had undergone a tuberculosis test in September 2015 that yielded a negative result. However, the nurse’s physician discovered TB in an X-ray taken while looking into an unrelated medical condition.

TB-causing bacteria can be spread from one person to another through the air. Symptoms include weakness, chest pain, fatigue, chills and fever, among others.